1. Field of the Invention
The present invention relates generally to a computer controlled creeling device for use in the carpet and textile industries, which device can intelligently move items in and around the manufacturing floor, and place bobbins where needed. Preferably, the device is an automated yarn creeling system for carpet tufting. The creeling device ultimately transfers packages of yarn from shipping pallets to the bullhorns of a creeler. The device determines the locations of empty packages, removes the empty packages and discards the empty cores, picks up and weighs full packages, and places the full packages on the empty bullhorn.
2. Background
A creel is a large rack or set of racks that holds several hundred spools or packages of yarn. Presently in the carpet and textile industries an individual, the creeler, is responsible for both the continuous running of the tufting machine, and most importantly, the replacement of empty packages on the creel with full packages. Packages are "skewered" through a central core in the package, wherein the core is typically a cardboard cylinder.
Carpet tufting plants typically use magazine-style creels. Each tufting machine creel has twice has many packages as needles or ends. A typical plant uses expanded creels that have both loading aisles and tying aisles. The creels have a set of rollers down the center of the loading aisles to move the shipping pallets, or full cases, of yarn packages. The creels are generally only two levels high.
No known automatic creeling system yet exists for the carpet tufting industry. Yet, an automated creeling device would improve the carpet manufacturing process by reducing the creel set-up time and cost, as well as decreasing the work-related injuries and waste produced by the current, manual system. Further, an automated creeling device would increase overall efficiency and improve the product quality, machine efficiency and the working conditions for the production workers involved in this process.
The job of creeling involves manually lifting full yarn packages (each weighing approximately 13 pounds) and placing them on the creel's bullhorns. Labor costs for performing this and related tasks can be quite high. Related tasks are, for example, finding and removing empty bobbins, replacing them with full packages of yarn, tying knots between the tail ends of running packages and the starting ends of the packages. In one carpet manufacturing plant, approximately 92 packages must be replaced every hour on a typical carpet tufting machine (that is, one every 39 seconds). In some instances, the creeler must lift the full packages as high as above his/her head while working on the creel. Therefore, a creeler may fully lift approximately 800 pounds of yarn per hour. This repeated motion can lead to work-related injuries, including metacarpal syndrome, and to high employment turnover rate. The automation of the creeling process would virtually eliminate this type of injury, among others, and its associated cost. Further disadvantages with the present job of creeling are the repetitive operation and servicing of the present creel system, which can lead to employee loss of interest and errors.
The textile industry has indicated that the level of efficiency during the third shift typically is lower than during the first and second shifts. Operator errors lead to lower quality goods and/or slower overall production rates. An automated creeler would run with the same efficiency 24 hours per day, and, thus, the level of efficiency would not depend nearly as much on the supply and quality of labor during shifts, especially the third shift.
Further, because yarn packages contain different lengths of yarns, the tufting creel may contain packages ranging from empty to near full, requiring a costly cut back operation to average the yarns among all packages, or downgrading the leftover yarns for lower grade carpet. An automated system should be capable of weighing and replacing individual packages to intelligently match lighter packages with heavier ones such that all the packages run out at approximately the same time at the conclusion of a yarn lot.
For simplification of description, there are generally four modes of operation in the creeling process: (1) normal operation; (2) changeover operation (used when changing to a new lot of yarn and removing all of the previous packages); (3) cut back operation (used when changing to a new lot of yarn without removing all of the previous packages); and (4) blow back operation (used when an end breaks).
In the normal operation of the creel, the individual creeler identifies empty packages on the bullhorns, manually removes and discards the empty packages, selects and places new packages on the bullhorns, and ties in each new package.
In the changeover operation, the creeler locates empty packages, replaces them with full packages from a new lot, and ties the leading yarn end of the new package to the trailing end of the package running on the opposite bullhorn.
The cut back operation involves a redistribution of packages that remain on the creel at the end of a lot and placing packages of the new lot yarn on the creel. This process allows the "easing in" of the new lot of yarn. The carpet that is made during this transition can be dyed light colors with little or no negative effect on the end product. Currently, the cut back operation requires approximately 15 man-hours to complete. During this time, the tufting machine is not running. There is also a backwinding process that is performed to make larger packages from the small packages left on the creel.
Finally, the blow back operation is necessary when a yarn breaks somewhere near the tufting machine or in the tube guiding the yarn. It involves blowing a yarn end from the tufting machine to the yarn package on the creel and tying it in.
3. Technical Approach
The carpet industry has indicated a need for the creeling operation to be automated to improve the efficiency and eliminate the job-related injuries associated with the present, manual creeling operation. To augment the initial designing of the present invention, two issues were studied. First, a method called `Matching` was developed and studied as a method to both reduce the amount of leftover yarns (residual yarns) at the end of a lot of carpet tufting and eliminate the cut back operation. Implementation of this method found that the inefficiencies in the creeling operation were greatly reduced. It was also found that this method could be implemented on the current creeling process performed by human workers, if proper personnel selection and careful job training were executed.
Second, the physical parameters and the servicing policies of the automated creeling device of the present invention were identified and determined through simulation studies. From those results, the design requirements of the present invention were specified.
Study of the placement of yarn packages and how they are replaced on the creel has indicated that the cut back operation can be eliminated or at least shortened with proper control over the placement of yarn. This type of controlled placement is implemented and monitored by the automated system of the present invention. This leads to time savings as well as reduction of waste.
The present invention automates the yarn package handling portion of the above modes of operation. Individuals are necessary for the tying step, which currently still must be completed manually. Therefore, with creeling automation, the following costs, among others, will be reduced or eliminated: labor, tufting machine down-time, health and injury related costs, yarn waste at the end of a yarn lot, operator errors, and operating training.
It should be noted that the creeling operation for the warping process in fabric manufacturing faces similar inefficiencies. Whereas in the carpet tufting process several yarns are fed from a creel to a tufting machine, in the warping process several yarns are fed from a creel to a large spool or beam. The yarns are wrapped around the beam parallel to each other. Eventually the yarns are fed off of the beam into a weaving loom. Thus, the creeling automation method and device disclosed herein can be extended to serve the textile industry as well.
To eliminate the cut back operation, the variation in package run-out times at each bullhorn was reduced. One way this was achieved was by manipulating the placement of packages so that the difference in the amount of yarn processed at each bullhorn pair was minimized. Since the weight deviation from package to package could not be controlled, it was compensated for at each pair of bullhorns by intelligently placing the packages so that the total package weight variation for each bullhorn pair was reduced. This was achieved by matching the package weights so that if the package that was currently running on one bullhorn was a "heavy" one, then a "light" package would be placed on the opposite bullhorn. By matching the package weights, the total sum of the weights of both packages was close to twice the average package weight. Obviously, these descriptive categories such as "heavy" were quantified in the simulation studies that determined the performance requirements of the present invention.
As the tufting machine took up yarn, the first set of packages placed ran out at widely varying times, but the second set of packages ran out at roughly the same time. The matching of the second set of package weights reduced the amount of residual, or left over yarn, on the creel at the end of a lot, thus eliminating the need for the cut back operation. Further, when deviation was reduced at each servicing, the distribution of run out times of the bullhorns was narrow. According to computer simulation studies, a narrow distribution of runout times allowed the automated creeler to service the creel faster and more efficiently. Because the automated creeler does not have to travel long distances to find the next empty package to service, there was a high probability of finding a package that needed to be serviced close to the one that was just serviced.
A first computer simulation study investigated the effect that matching package weights had on reducing the amount of residual yarn left on a creel after 12 package replacements. First, 12 sets of 960 numbers randomly chosen from a normal distribution with a mean of 13 pounds and standard deviation of 0.5 pounds were created. These numbers represented an actual carpet tufting operation having a yarn lot size of approximately 100,000 yarns and 960 yarns across the width of the carpet. Each set was classified into 2 (heavy and light), 3 (heavy, medium, light), 4 (heavy, medium, medium light, light), and 5 (very heavy, heavy, medium, light and very light) classes. Categorization of 960 classes was achieved by arranging the data set such that the heaviest package from the first set was matched with the lightest of the next set, the second heaviest package was matched with the second lightest of the next set, and so forth. The `no class` category represented the random placement of packages without consideration for weight deviation, which is the current placement scheme.
Next, at every even package replacement (second, fourth, etc.), the opposite weight was placed at each bullhorn to minimize the standard deviation of the distribution of yarn weight across the creel. For example, if bullhorn #12 had a heavy package from the first set, then a light package was placed from the next set at the bullhorn. After every replacement, the bullhorn that had the lightest total weight of yarn placed was identified, and the total differences between that minimum value and the total weight run at each bullhorn was calculated. The sum of these differences was termed the total residual yarn and it represents the yarn remaining on the creel after the first package is empty.
FIG. 9 and Table 1 illustrate the total residual yarn after each replacement of packages for a creel with 960 bullhorns. FIG. 9 represents the average of the five experiments. The total residual yarn is plotted against the number of package replacements for six different weight categories. In FIG. 9, the total residual yarns are compared after each replacement. From this Figure, there were several discoveries. First, this Figure shows the expected result of a reduction in total residual yarn by applying a larger number of classes. The second expected result is the zigzag lines, or the fluctuation of total residual yarn, by applying the matching methods. The fluctuation of total residual yarn occurred because the package weight classes at an even number of replacements (second, fourth, etc.) were matched with the odd number of replacements, thus decreasing the residual yarn at each even replacement.
TABLE 1 No 2 3 4 5 960 classes classes classes classes classes classes Replacements (lb) (lb) (lb) (lb) (lb) (lb) 1 1422.3 1422.3 1422.3 1422.3 1422.3 1422.3 2 2093.2 1632.1 1283.5 1227.8 1161.7 220.5 3 2618.9 2122.7 2060.1 1860.9 1890.3 1600.2 4 2905.3 1935.7 1731.0 1565.6 1731.4 245.5 5 3175.9 2566.1 2421.2 2057.2 2096.8 1574.7 6 3507.6 2336.0 2052.2 1645.3 1850.4 304.1 7 3779.3 2637.3 2768.3 2337.2 2371.1 1551.6 8 4208.0 2761.0 2428.6 1914.7 1979.1 409.6 9 4573.7 3024.8 3062.0 2791.8 2662.2 1632.8 10 4949.2 3165.3 2771.4 2406.5 2262.3 443.3 11 5033.2 3395.9 3259.9 2953.0 2924.1 1645.3 12 5302.6 3568.8 2971.2 2409.5 2689.5 370.8